A deterministic verification engine for agents. Fires the edge cases your sandbox never sends — duplicate webhooks, declined cards, rate limits — then proves a fix: the same scenario fails on the old code and passes on the new. npm: fetchsandbox-mcp
Setup
Choose your client, copy the config, then fill in any required environment variables.
Local
claude mcp add fetchsandbox --env FETCHSANDBOX_API_KEY='<FETCHSANDBOX_API_KEY>' -- npx -y fetchsandbox-mcp~/.codex/config.toml
[mcp_servers.fetchsandbox]
command = "npx"
args = ["-y", "fetchsandbox-mcp"]
env = { FETCHSANDBOX_API_KEY = "<FETCHSANDBOX_API_KEY>" }
# codex mcp add fetchsandbox --env FETCHSANDBOX_API_KEY='<FETCHSANDBOX_API_KEY>' -- npx -y fetchsandbox-mcp~/.cursor/mcp.json
{
"mcpServers": {
"fetchsandbox": {
"command": "npx",
"args": [
"-y",
"fetchsandbox-mcp"
],
"env": {
"FETCHSANDBOX_API_KEY": "<FETCHSANDBOX_API_KEY>"
}
}
}
}.vscode/mcp.json
{
"servers": {
"fetchsandbox": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"fetchsandbox-mcp"
],
"env": {
"FETCHSANDBOX_API_KEY": "<FETCHSANDBOX_API_KEY>"
}
}
}
}~/.gemini/settings.json
{
"mcpServers": {
"fetchsandbox": {
"command": "npx",
"args": [
"-y",
"fetchsandbox-mcp"
],
"env": {
"FETCHSANDBOX_API_KEY": "<FETCHSANDBOX_API_KEY>"
}
}
}
}claude_desktop_config.json
{
"mcpServers": {
"fetchsandbox": {
"command": "npx",
"args": [
"-y",
"fetchsandbox-mcp"
],
"env": {
"FETCHSANDBOX_API_KEY": "<FETCHSANDBOX_API_KEY>"
}
}
}
}.trae/mcp.json
{
"mcpServers": {
"fetchsandbox": {
"command": "npx",
"args": [
"-y",
"fetchsandbox-mcp"
],
"env": {
"FETCHSANDBOX_API_KEY": "<FETCHSANDBOX_API_KEY>"
}
}
}
}Remote
claude mcp add --transport http fetchsandbox https://fetchsandbox.com/mcp/v1~/.codex/config.toml
[mcp_servers.fetchsandbox]
url = "https://fetchsandbox.com/mcp/v1"
# codex mcp add fetchsandbox --url https://fetchsandbox.com/mcp/v1~/.cursor/mcp.json
{
"mcpServers": {
"fetchsandbox": {
"url": "https://fetchsandbox.com/mcp/v1"
}
}
}.vscode/mcp.json
{
"servers": {
"fetchsandbox": {
"type": "http",
"url": "https://fetchsandbox.com/mcp/v1"
}
}
}~/.gemini/settings.json
{
"mcpServers": {
"fetchsandbox": {
"httpUrl": "https://fetchsandbox.com/mcp/v1"
}
}
}claude_desktop_config.json · Customize › Connectors › Add custom connector
{
"mcpServers": {
"fetchsandbox": {
"command": "npx",
"args": [
"-y",
"mcp-remote",
"https://fetchsandbox.com/mcp/v1"
]
}
}
}.trae/mcp.json
{
"mcpServers": {
"fetchsandbox": {
"url": "https://fetchsandbox.com/mcp/v1"
}
}
}Environment variables
FETCHSANDBOX_API_KEY
Replace the placeholders with your own credentials and keep them out of version control.